Assessment of heart failure and left ventricular systolic dysfunction after cardiac pacing in patients with preserved left ventricular systolic function.

BACKGROUND: There is an accumulating data suggesting the deleterious effects of right ventricular pacing on left ventricular performance. Such pacing mimics left bundle branch block resulting in a prolonged QRS duration and causes ventricular asynchrony. AIMS: The purpose of this study is to assess heart failure and left ventricular systolic function after cardiac pacemaker implantation in patients with atrioventricular block and preserved systolic left ventricular function. Secondly, we sought to search for predictive factors of developing left ventricular dysfunction after pacing.
METHODS: In this prospective study, we included patients who had been implanted for at least six months. They underwent medical history and examination, 12 leads electrocardiogram and echocardiography before pacemaker implantation and when attending to routine pacemaker follow up.
RESULTS: Forty-three patients (22 men and 21 women, age 71+/-12 years) were included in this study. Twenty-nine patients had DDD pacing and 14 VVI pacing. The ventricular lead was implanted in the apex in all patients. After a median follow up of 18+/-11 months, 11 patients (25%) developed signs of congestive heart failure. NYHA was higher after implantation (1.64+/-0.7 versus 2.27+/-0.8, p>0.00001). Left ventricular ejection fraction decreased significantly during follow up (60+/-6% versus 51+/-13%, p=0.0002). Eleven (25%) patients developed left ventricular dysfunction. We compared patients who had left ventricular ejection fraction (LV EF) less or equal to 40% (group A) and patients having LV EF greater than 40% (group B) after implantation. Patients in group A had a paced QRS width significantly larger than group B (181+/-32 ms versus 151+/-26 ms, p=0.002), a significantly prolonged intra left ventricular electromechanical delay (115+/-59 ms versus 45+/-35 ms, p<0.0001) and interventricular delay (44+/-29 ms versus 27+/-18 ms, p=0.02). Age, sex, diabetes hypertension, pacing mode and percentage of ventricular pacing were similar in both groups. A paced QRS width of 180 ms had the best sensitivity and specificity for detecting left ventricular dysfunction: sensitivity=54% and specificity=93%, p=0.01, area under the curve=0.75.
CONCLUSION: Patients with atrioventricular block and preserved left ventricular systolic function at baseline decrease significantly left ventricular ejection fraction after pacing. Induced ventricular asynchronism plays a major role in the deterioration of left ventricular function. Prolonged paced QRS width is a good predictor of left ventricular dysfunction after pacing. Larger prospective studies are needed to confirm these data.